Prostheses such as stent grafts as used for stenting or repairing aneurysms as in the abdominal or thoracic aorta are usually fairly effective at excluding the aneurysm from exposure to blood pressure and therefore protect the patient from the dangers of aneurysm rupture. However, these stent grafts frequently block the flow of blood to the side branch vessels that carry blood to other organs and anatomy. The occlusion of the side branch vessels can result in damage to the tissue perfused by the blood flow from the side branch vessel.
Attempts to deal with these occlusions have been such things as by-pass vessels placed surgically to restore blood flow from a region of the aorta that is not stented and the placement of holes or fenestrations in the stent grafts that are aligned with the side branch vessel so asto allow blood to continue to flow into the side branch vessel. The fenestration approach is the preferred method since it does not involve major vascular surgery. Patients receiving stent grafts usually do so because they are too weak or sick to endure surgery. Once the fenestrated stent graft is deployed, the stent graft is anchored to the ostium of the side branch with a balloon expanded stent. This stent is placed so that the bulk of the stent length is in the side branch with 1 or 2 mm extending into the lumen of the stent graft. The 1 or 2 mm segment is then over expanded, or flared slightly, to hold the stent graft to the aortic wall and effect a seal that prevents blood from flowing into the aneurysm.
While this balloon stenting through a fenestration process is fairly effective, it is deficient in that the connection between the balloon expanded stent and the stent graft at the fenestration is never completely snug or tight. As a result, leaks often occur between the stent graft and aortic wall. The reason this connection can never truly be a tight, zero clearance fit is because balloon expandable stents always have some amount of recoil after they are expanded by the delivery balloon. This recoil is usually 4% to 10% of the stent diameter attained prior to balloon deflation. As a result, the fit between the balloon expandable stent and the stent graft fenestration is never truly tight. The eventual endothelialization of the area around the fenestration and the ostium or origin of the side branch is the only hope of an eventual complete seal and exclusion of the aneurysm. Before endothelialization occurs, the patient is still at risk of a ruptured aneurysm. In some cases, where the gap between the stent graft and aortic wall is large, a seal at the fenestration may never occur, leaving the patient with minimal or no protection from a ruptured aneurysm.
Other exemplary prostheses including stents, grafts, and stent grafts with, for example, fenestrations are disclosed in U.S. Pat. Nos. 6,524,335; 5,984,955; 6,395,018; 6,325,826; 6,077,296; 6,030,414; 5,617,878; 5,425,765; and 4,580,569, all of which are incorporated herein by reference in their entirety.